...I think there's no point of rendering so huge images; it takes too long to render...
Actually, depending on the scene content and level of model complexity, one way to get around long --- anti-aliased --- render times is to render large-format images without AA. Then, you can get the effect of AA after post-processing to a smaller (or at least "more reasonable") size. Of course, this doesn't always produce equivalent results, but it's a trade-off worth considering.
BTW, adamsbullock, your scene is very interesting. Your robots are very '30's, Buck Rogers-ish, and I like the attention you gave to routing plumbing and cables. What are the little articulated "critters" on the ground? Looks like something I need to wear steel-toed shoes around!